Head gasket bore size

[tossaxe]

Hello,

The time has come for me to install a steel head gasket. Yet can't find the answer WHY aren't there any steel gaskets with 86 bore? Tomei, Apexi, Cosworth etc all as you know start with 87. Why is this? Do the folded edges of MLS gaskets expand when compressed? Hard to believe that 0.5mm void ring formed in the cylinder wall by a +1mm bore gasket isn't detrimental to the performace of the engine..

[BlackZenkiS14]

I'm 99% sure I got an 86.5 Apexi one when I did my motor build.

[NismoR003]

yeah could never find one either, yeah i think it does expand when compressed

[tossaxe]

If the gasket do expand, that's fine- means my search for an 86 are over. Yet it's quite misleading. Someone with 87 bore block would screw their engine installing a gasket "for an 87 bore" if it does expand. And how would you know the final bore size of the gasket.. different diameters would expand differently.

[Bryants95240sx]

Thought it was common knowledge that you go 1mm bigger than ur bore? At least that's what I did....

[Datspar]

LOL no it isn't detrimental to performance, it makes no difference. It's far safer to be oversized on the gasket bore than under. Oversized = tiny bit more volume which equates to almost no difference. Undersized (hanging in bore) = burnt headgasket. You decide which way you'd rather be...

[tossaxe]

Well thought such high tech sheets of metal would be the exact size as the manufacturer states.
Anyway, I asked cause I did not know, never intended to argue with anyone about this :)
Than You All ;) 87 it is